1. Field of the Invention
The present invention generally relates to apparatus, methods, and systems for treating storm water and removing sediment and suspended solids in water discharged from construction, building and other sites where the discharge of suspended solids into riparian systems or storm drain systems is to be avoided, and, more particularly, to separating sand, oil, biomass, and other debris from water and reducing the amount of nutrients and nitrogen compounds in treated water. More broadly, the present invention relates to apparatus, methods, and systems for treating high volumes of liquids, mixtures, suspensions and the like to separate them into constituent parts; and for processing liquids, mixtures, suspensions and the like to remove solids and discharge water with less suspended solids.
2. Relevant Background
Modern storm drainage systems involve directing storm water to storm or sewer drains where the water is collected for later processing and disposal or simply discharged into larger bodies of water. In those systems, storm water is guided to flow from slopes and streets into the storm drains by the force of gravity. During that flow, storm water may pick up debris, trash (e.g., paper, cans, and cigarette butts), biomass (e.g., grass, leaves, excrement and discarded food), silt, sand, stone, oil, pollutants, heavy metals, and discarded medical devices and personal products (e.g., used needles and condoms) and other particles. Further, the storm drainage systems may also collect other run-off water such as water used for irrigation. Storm water and run-off water may naturally flow through soil or other terrains and pick up organic matter or chemicals, such as plants, leaves, hydrocarbons, nitrates, or other compounds.
There is a great deal of interest in effectively processing storm water. Drainage systems usually flow into natural water systems, such as oceans, lakes, rivers, streams, and other similar bodies of water. It would help protect the environment if there was a realistic, cost-effective capability to separate out man-made and natural contaminants and pollutants before the drainage is directed into the natural water systems and avoid upsetting the natural ecological balance of such systems. Further, if storm water and other run-offs can be effectively treated and recaptured as clean water, or at least as gray water, there is a potential that the recaptured water can help satisfy domestic needs for water.
There is also considerable interest in treating fluids for mining, agriculture, and industrial use. Besides the treatment and purification of water, the products separated from the fluid during treatment may be of value. For example, minerals in run-offs from mining or farms that contain high nutrient contents, various constituents of lubricants, and the like may be separated, collected, and reused or recycled. Further, the recovery of fluids or solids in industrial applications and from waste streams may be of interest.
Construction and building sites frequently collect or produce significant amounts of storm water runoff, containing high levels of suspended solids, that needs to be pumped away from the site. Riparian and storm drain systems may be unable to accommodate the discharged fluid, especially the large amount of sediment that may be deposited. In order to protect the environment near such sites, government regulations may require that water from the sites be processed beforehand to reduce the amount of suspended solids that is discharged. Typically, the discharged water is not environmentally hazardous but may contain gravel, dirt, sand, clay, and other suspended solids that need to be removed or reduced in concentration. After removing or reducing the concentration of the suspended solids, the processed water may be suitable for discharge into a nearby water system.
Storm water runoff and groundwater are typically stored in a pond on site which may slowly evaporate or soak into the surrounding earth. Such ponds may overflow onto roads, into streams, across property, and into low lying areas causing flooding and depositing large amounts of sediment.
The process of removing suspended solids from large volumes of water stored at construction and building sites is frequently called “dewatering.” The usual method of dewatering involves the use of a dewatering bag. Dewatering bags, also known as dirt bags, gravity bag filters, and sediment filter bags are simply large, rectangular filter bags fed by one or more sources of water needing treatment. A pump is typically used to move water from a storage pond to feed the dewatering bag.
The water flows into the interior of the bag and passes through the wall of the bag. The wall of the bag filters out solids of a particular size. The water leaches through the surface of the bag to the surrounding environment. In essence, dewatering bags are large filters that separate suspended solids from the water. The bag fills with solids and then may be discarded.
The appropriate size of a dewatering bag for a particular application is generally determined by the flow rate and components in the water that needs to be processed. The amount of solids in the water can affect the size of the dewatering bag needed because a large sediment burden will more quickly fill a bag and clog the pores in the bag material. Certain solids, like clay, will clog dewatering bags very quickly.
In estimating the appropriate size of the dewatering bag for a particular application, a selected bag that is too large for the task wastes money and takes up valuable space at the site while a bag that is too small for the task will necessitate the use of multiple dewatering bags, a schedule for monitoring and replacing those bags, and the time, effort, and expense of actually monitoring and replacing the extra bags.
Moreover, variations in the flow rate and the components in the water pumped from the site may necessitate the acquisition of an inventory of bags to accommodate those variations. If a high flow rate is desired, a larger dewatering bag (e.g., fifteen feet by fifteen feet) may be deployed, or multiple dewatering bags may be fed by a manifold of hoses in parallel, or a dewatering “tube” that can be hundreds of feet long may be deployed. These large bags and tubes are cumbersome, expensive, and will, due to the weight of the water and collected sediment exert a great load on the surface. Such loads can be detrimental to the ground and other surfaces. The flow of water through the bag (or tube) may also cause erosion in the surrounding area in a pattern that may be difficult to predict.
Another problem with dewatering bags is that they are usually designed to be used only once before being discarded. The use of a disposable dewatering bag is not environmentally-friendly because the bag, with or without its contents, is typically made of a synthetic material that will need to be disposed. In addition, a filled bag lying on the ground will require heavy machinery to move. It may be impossible to move a bag that is partially filled without ruining it. Reusable bags present the difficulty of transporting the heavy bag and removing a heavy load of sediment from a relatively fragile bag.
The fragility of a dewatering bag presents issues as well. A bag can be punctured or torn at a construction site by the surface on which it is placed or by inadvertent contact with machinery. As it fills, dewatering bags may stretch to adopt a different footprint. A bag that is filled or exposed to excessive water pressure may burst. At high pressures, the bursting of a bag could become a dangerous explosion of water and sediment.
Better methods and systems are needed for dewatering large quantities of fluid to remove suspended solids.
U.S. Pat. No. 7,311,818 to Gurfinkel discusses an approach to a water separation unit having an inner and outer housing for storm water collection. Storm water enters the inner housing where water and debris are supposed to be separated. A series of hollow tubes connect the inner housing to the outer housing to allow liquid to pass into and collect in the outer housing and flow out of the unit through a network of discharge pipes. One problem with that approach is that the tubes can be clogged with debris. Another problem with that approach is that most of the silt and sand is not collected at the tube level in the inner housing; rather, it flows through the tubes and can be drawn into the discharge pipe and exit the outer housing. Yet another problem with that approach is that the unit must be completely drained before cleaning.
U.S. Pat. No. 7,846,327 to Happel, commercialized as the Nutrient Separating Baffle Box from Suntree Technologies, discusses an approach to a storm water filter box having a fixed basket to collect debris and a floatable skimmer to prevent floating debris that passed through the basket from leaving the box. The skimmer is positioned within the box between the inlet and the outlet and rises and falls with the water level in the box. Storm water is directed to pass through the basket to the skimmer where floating debris is collected. One problem with that approach is that moving parts that can break or jam are required for the skimmer to move. Another problem is that floating debris stays in contact with the wastewater, promoting decomposition of the debris.
U.S. Pat. No. 7,857,966 to Duran discusses an approach to a storm water inlet apparatus having inlet and outlet pipes on level with each other where wastewater flows directly through a catch basin. The apparatus includes a hood and skirted boom affixed to an interior wall of the basin over the outlet pipe. Wastewater flows beneath the hood and skirted boom and out through the outlet. In the process, heavier-than-water sediments sink to the bottom of the basin while lighter-than-water debris floats on top of the wastewater in the basin. One problem with that approach is that a sealed hood prevents airflow, allowing a siphon to develop and pull the level of the wastewater down and potentially draw in the floating debris, thus reducing the performance of the apparatus. Also, the debris stays in contact with the wastewater, promoting decomposition of the debris.
U.S. Pat. No. 7,780,855 to Eberly discusses an approach to a system for storm water treatment. A treatment unit is connected to a control chamber through which fluid flows. The fluid is diverted via a control partition to an inlet pipe into the unit for treatment and returned through an outlet pipe. If the fluid flow exceeds the capacity of the inlet pipe, excess fluid flows over the control partition to the outlet of the control chamber. A problem with the approach is that it is not well-suited for a retrofit application due to the lack of significant grade between the inlet and outlet of the control chamber. Another problem with that approach is that there is no separation between different types of debris, i.e. biomass, hydrocarbons, silt and sand, etc.; everything is mixed in a potentially toxic soup.
U.S. patent Ser. No. 10/430,170 to Peters et al. discusses a system for removing contaminants from storm water. Storm water flows through a process chamber comprising a series of vertical baffles that extend from the top, bottom, and sides of the chamber. Storm water flows through the chamber around the baffles, and debris is trapped along the bottom of the chamber and by filters placed in the gaps between the baffles and the chamber. One problem with that approach is that all filtration is done in the water; thus, debris stays in contact with the water promoting decomposition of the debris. A further problem with that approach is that all debris is collected at the bottom of the chamber, limiting the capacity of the chamber for collecting debris. Another problem with that approach is that the relatively small gaps between the baffles and the chamber may become easily clogged with debris.
There is further need for an efficient, cost-effective apparatus methods and systems for separating storm water, operating fluids, lubricants, coolants, wastewater and the like to separate out solids, hydrocarbons, contaminants and pollutants, and recapture and recycle desired components.